This Program Project focuses on mechanisms and therapy of electrical dysfunction of the heart, particularly those rhythm disturbances which have lethal potential. The projects are grouped under four sections: Electrophysiology, Cellular and Subcellular; Metabolism: Relationship to Electrical Function; Myocardial Blood Flow: Relationships to Electrophysiology and Clinical Arrhythmias; and Anatomic and Hemodynamic Environment of Arrhythmias. It is the aim of the Program Project to foster integrated studies in the above areas in order that the information derived will have clinical applicability and will be exchangeable across interdisciplinary lines.